EP 1276231 A3 20040114 - Variable gain amplifier
Title (en)
Variable gain amplifier
Title (de)
Verstärker mit variabler Verstärkung
Title (fr)
Amplificateur à gain variable
Publication
Application
Priority
JP 2001209702 A 20010710
Abstract (en)
[origin: EP1276231A2] A variable gain amplifier is provided with a first differential amplifier circuit (4) and a second differential amplifier circuit (6) each formed with transistors. A common signal is inputted to each of the differential amplifier circuits (4, 6), and output signals of the differential amplifier circuits are added together for output via resistances. When a voltage of a variable voltage source (Vc) is increased, a bias current of the first differential amplifier circuit (4) having a high gain is increased, and therefore the gain of the first differential amplifier circuit (4) is raised, resulting in an increase in overall gain. When the voltage of the variable voltage source (Vc) is decreased, a bias current of the second differential amplifier circuit (6) having a low gain is increased and therefore the gain of the second differential amplifier circuit (6) is raised, so that the second differential amplifier circuit (6) has greater effect and thus provides an amplifier circuit with a high saturation input level. The bias current of the second differential amplifier circuit (6) is decreased when the gain of the variable gain amplifier is raised, and the bias current of the first differential amplifier circuit (4) is decreased when the gain is lowered, whereby power consumption can be reduced. <IMAGE>
IPC 1-7
IPC 8 full level
CPC (source: EP US)
H03G 1/0023 (2013.01 - EP US)
Citation (search report)
- [X] US 4227256 A 19801007 - O'KEEFE GERALD T
- [X] EP 0730345 A2 19960904 - NEC CORP [JP]
- [X] EP 0317759 A2 19890531 - TEKTRONIX INC [US]
Designated contracting state (EPC)
AT BE BG CH CY CZ DE DK EE ES FI FR GB GR IE IT LI LU MC NL PT SE SK TR
DOCDB simple family (publication)
EP 1276231 A2 20030115; EP 1276231 A3 20040114; JP 2003023331 A 20030124; JP 3704703 B2 20051012; US 2003034841 A1 20030220; US 6891405 B2 20050510
DOCDB simple family (application)
EP 02291736 A 20020710; JP 2001209702 A 20010710; US 19145502 A 20020710